Thermoelectric (TE) nanocomposite material that includes at least one component consisting of nanocrystals. A TE nanocomposite material in accordance with the present invention can include, but is not limited to, multiple nanocrystalline structures, nanocrystal networks or partial networks, or multi-component materials, with some components forming connected interpenetrating networks including nanocrystalline networks. The TE nanocomposite material can be in the form of a bulk solid having semiconductor nanocrystallites that form an electrically conductive network within the material. In other embodiments, the TE nanocomposite material can be a nanocomposite thermoelectric material having one network of p-type or n-type semiconductor domains and a low thermal conductivity semiconductor or dielectric network or domains separating the p-type or n-type domains that provides efficient phonon scattering to reduce thermal conductivity while maintaining the electrical properties of the p-type or n-type semiconductor.